Unit 1- Bonding, Structure And Properties

Question 1

What is a compound?

Answer 1

Substances in which two or more elements are chemically combined.

Question 2

What is an ionic bond ?

Answer 2

Bonding present in ionic bonding.

Question 3

What is a metallic bond ?

Answer 3

Bonding present in metals.

Question 4

What is a covalent bond ?

Answer 4

Bonding present in giant covalent structures and simple covalent molecules

Question 5

What is the bonding and structure like with ionic compounds ?

Answer 5

-Metals and non metals
-electrostatic attractions between oppositely charged ions
-ions form a giant ionic lattice structure
-metal atoms lose electrons to become positively charged ions
-non metal atoms gain electrons to become negatively charged ions

Question 6

How can you show the electron transfer of an ionic compound ?

Answer 6

Dot and cross diagrams.

Question 7

What are the properties of ionic compounds ?

Answer 7

-Strong electrostatic attraction between oppositely charged ions means ionic compounds have high melting and boiling points
-When solid ionic compounds don’t conduct electricity because the ions are fixed in place
-ions can move when molten/dissolved so then ionic compounds conduct electricity
-they’re brittle

Question 8

What is the bonding and structure like in metallic compounds ?

Answer 8

-metals consist of giant structures of positive metal ions
-electrons in outer shell of metal atoms are delocalised and so are free to move through the whole structure
-metallic bonds form due to the electrostatic attraction between the positively charged metal ions and negative delocalised electrons

Question 9

What are the properties of metallic compounds ?

Answer 9

-layers of ions in metals are able to slide over each other, so metals can be bent and shaped making them malleable and ductile
-delocalised electrons can move through the metal and carry charge, so metals conduct electricity and heat
-metallic bonds are very strong and require large amounts of energy to be broken- high melting and boiling points

Question 10

What happens during covalent bonding ?

Answer 10

-When atoms share pairs of electrons
-These bonds are strong.

Question 11

What are the two types of covalent structures ?

Answer 11

-Simple molecules
-Giant covalent structures

Question 12

What are simple molecules like ?

Answer 12

-Substances consisting of simple molecules are usually gases or liquids that have low boiling and melting points
- substances consisting of them have weak intermolecular forces (forces holding atoms together) which are broken in boiling and melting- not the covalent bonds
-intermolecular forces increase with the size of the molecules so larger molecules have higher melting and boiling points
-don’t conduct electricity because simple molecules do not have an overall charge

Question 13

What are giant covalent structures like ?

Answer 13

-substances with giant covalent structures are solids with high melting points
-atoms in structure are linked to other atoms by strong covalent bonds

Question 14

What are diamond and graphite both ?

Answer 14

-Allotropes of carbon
-allotropes are different forms elements can exit in

Question 15

What are diamonds like ?

Answer 15

-each carbon is joined to 4 others covalently
-4 is the maximum number of bonds each carbon atom can make
-it’s very hard and has a very high melting point
-does not conduct electricity

Question 16

What is graphite like ?

Answer 16

-each carbon is covalently bonded to 3 other carbons forming layers of hexagonal rings with no covalent bonds between layers
-these layers can slide over eachother so they have weak intermolecular forces (meaning graphite is soft and slippery)
-one electron for each carbon atom is delocalised which makes graphite similar to metals because of its delocalisation electrons
-it can conduct electricity unlike diamonds

Question 17

Whats graphene ?

Answer 17

-single layer of graphite
-has properties that make it useful in electronics

Question 18

What are fullerenes ?

Answer 18

-molecules of carbon atoms with hollow shapes
-used for lubricants, to deliver drugs in the body and catalysts

Question 19

What are carbon nanotubes ?

Answer 19

-Cylindrical fullerenes with very high length to diameter ratios (slender)
-properties make them useful for nanotechnology, electronics and materials
-used for reinforcing materials for example tennis rackets

Question 20

What are the properties of nano particles ?

Answer 20

-1-100 nanometres across
-contain a few hundred atoms
-different properties to the ‘bulk’ chemical it’s made from

Question 21

What are some nanoparticles and their uses?

Answer 21

-nano silver- kills bacteria so it’s used in wounds dressing and Deodorant, also used to like socks and fridges to kill bacteria causing bad smells
-nano titanium oxide- these nano particles are so small they do not reflect visible light so they cannot be seen. They’re used in sunblock creams to block harmful ultraviolet light without appearing white on the skin

Question 22

What are the risks of nanoparticles ?

Answer 22

-so small they could potentially enter the blood stream and many feel the risk of them aren’t yet known so more testing should be done before they’re used
-long term effects not know as a relatively new material
-could enter and potentially damage the environment

Question 23

What are some smart materials ?

Answer 23

-Shape memory alloys/polymers- can be bent and deformed but return to their original shape when heated. Shape memory polymers are used in sport equipment like gum shields. Shape memory alloy used are plates for bone fractures and car bodies.
-Thermochromic materials-change colour when they reach a certain temperature and used in mugs and spoons
-Photochromic pigments- change colour when exposed to light. For example sunglasses that darken when in bright sun
-polymer gels- hydrogels absorb 1000 times their volume in water. Certain stimuli (water or change in pH) can cause water to be released. Used in nappies, fake snow and hair gel